1. Field of the Invention
This invention relates to an ink ribbon. More specifically, this invention relates to an ink ribbon which is applicable to, for example, a printing apparatus for printing color pictures on a printing medium, such as card or the like, using a thermal dye copy system.
2. Description of the Related Art
Heretofore, a card printing apparatus has been proposed (Japanese Patent Application Laid Open No. 11370/1987), in which a plurality of coloring matters for printing made up of dyes, such as yellow, magenta, and cyan which have been applied on an ink ribbon at regular intervals, are thermally transferred by a thermal printing head onto a card type printing medium (hereinafter, referred to as a "card") so as to overlay one on the other, whereby a color picture is printed on the card. This printing is based on color picture information optically read from a color photograph, a color picture picked up by a video camera, or the like.
As shown in FIG. 1, the ink ribbon 1 to be used in the above type of card printing apparatus, is such that the yellow coloring dye Y, the magenta coloring dye M, and the cyan coloring dye C have been respectively arranged at predetermined intervals to make up a printing unit for one page. A unit header mark PH, which has the same width as the ink ribbon 1 and which has a predetermined length H1, is located at the head portion of this particular page printing unit, that is to say, at the head of the yellow coloring dye Y. The magenta color mark MH and the cyan color mark CH which respectively have predetermined lengths H2 and H3 and widths which are half the width of the ink ribbon 1, are located on one side of the longitudinal center of the ribbon, and are arranged at the respective heads of the magenta coloring dye M and the cyan coloring dye C.
The ink ribbon driving system of this card printing apparatus has first and second sensors 2A and 2B which are positioned so as to monitor each half-portion of the ribbon width. Thus, in this ink ribbon driving system, when the first and second sensors 2A and 2B sense the mark at the same time, it is indicated that the head of one page has been detected, while when only the first sensor 2A senses the mark, the head of a color is determined. In this way, the position of a plurality of different colored dye portions can be accurately determined and high quality printing can be performed without the adverse effects of ribbon length and slip, etc.
With this type of card printing apparatus, there are some instances where it is particularly desired to print only black letters or even a bar code (which can be read by a bar code reading unit such as that utilizing an infrared sensor) in addition to the color printing using three colors Y, M, and C. Therefore, an ink ribbon on which a black coloring dye is applied in addition to the yellow coloring dye Y, the magenta coloring dye M, and the cyan coloring dye C, is used.
In such a ink ribbon, a black color mark is put at the head of the black coloring dye. However, this introduces a problem that with only a simple construction, which utilizes only two sensors 2A and 2B to sense the marks and to provide the required timing, it is not possible to distinguish between the black coloring dye and the unit header mark PH. Therefore, it has been proposed that the sensor output obtained from two sensors be processed based on the width of mark used to denote the coloring dyes Y, M, and C to determine the header detection. However, this process complicates the ink ribbon driving system and the associated computation circuitry, and inhibits simplification and miniaturization.
Furthermore, in such a printer, it is extremely helpful if the winding diameter of the ink ribbon can be determined.